Greenhouse Introduction types and Microclimate components

1. 8.Green House

5. పెైరు పెరుగుదలకు కావలసినవి
 ఉష్ణో గరత :- 18-30℃
 గాలిలో తేమ :- 50-70%
 Co2 :- 300-800ppm(Parts per
Milion)
 సూరయరశ్మి. :- 400-700 nm(nano meter)
మట్టిలో సూక్ష్ిజీవులు

7.  After the advent of green revolution, more emphasis is laid on the quality of the
product along with the quantity of production to meet the ever- growing food
requirements. Both these demands can be met when the environment for the plant
growth is suitably controlled. The need to protect the crops against unfavorable
environmental conditions led to the development of protected agriculture.
Greenhouse is the most practical method of achieving the objectives of protected
agriculture, where the natural environment is modified by using sound
engineering principles to achieve optimum plant growth and yields.

8.  A greenhouse is a framed or an inflated structure covered with a transparent or
translucent material in which crops could be grown under the conditions of at least
partially controlled environment and which is large enough to permit persons to
work within it to carry out cultural operations.
 Protected agriculture was fully established with the introduction of polyethylene
after the World War II. The first use of polyethylene as a greenhouse cover was in 1948,
when professor Emery Myers Emmert, at the University of Kentucky, used the less
expensive material in place of more expensive glass.

9.  The total area of glasshouses in the world (1987) was estimated to be 30,000 ha and most of
these were found in North- Western Europe. In contrast to glasshouses, more than half of the
world area of plastic greenhouses is in Asia, in which China has the largest area. According to
1999 estimates, an area of 6, 82,050 ha were under plastic greenhouses (Table). In most of the
countries, green houses are made of plastic and glass; the majority is plastic.
 Glasshouses and rigid plastic houses are longer-life structures, and therefore are most located
in cold regions where these structures can be used throughout the year. In Japan, year-round use
of greenhouses is becoming predominant, but in moderate and warm climate regions, they are
still provisional and are only used in winter. In India, the cultivation in the plastic greenhouses is
of recent origin. As per 1994-95 estimates, approximately 100 ha of India are under greenhouse
cultivation.

10. Region Area (ha)
Europe 1,80,000
Africa and the Middle East 55,000
America 22,350
Asia
China - 3,80,000
Japan – 51,042
Korea – 2,200
4,50,000
World Total 6,82,050
Estimated world use of plastic greenhouses (1999)

11. Since 1960, the greenhouse has evolved into more than a plant
protector. It is now better understood as a system of controlled
environment agriculture (CEA), with precise control of air and root
temperature, water, humidity, plant nutrition, carbon dioxide and light.
The greenhouses of today can be considered as plant or vegetable
factories. Almost every aspect of the production system is automated,
with the artificial environment and growing system under nearly total
computer control.

12. Greenhouse Effect
 In general, the percentage of carbon dioxide in the atmosphere is 0.035% (345 ppm). But, due to the emission
of pollutants and exhaust gases into the atmosphere, the percentage of carbon dioxide increases which forms a
blanket in the outer atmosphere. This causes the entrapping of the reflected solar radiation from the earth surface.
Due to this, the atmospheric temperature increases, causing global warming, melting of ice caps and rise in the ocean
levels which result in the submergence of coastal lines. This phenomenon of increase in the ambient temperature,
due to the formation of the blanket of carbon dioxide is known as greenhouse effect.
 The greenhouse covering material acts in a similar way, as it is transparent to shorter wave radiation and opaque
to long wave radiation.
 During the daytime, the shorter wave radiation enters into the greenhouse and gets reflected from the ground
surface. This reflected radiation becomes long wave radiation and is entrapped inside the greenhouse by the covering
material. This causes the increase in the greenhouse temperature. It is desirable effect from point of view of crop
growth in the cold regions.

13. Advantages of Greenhouses:
 The following are the different advantages of using the green house for growing crops under
controlled environment:
1. Throughout the year four to five crops can be grown in a green house due to availability of
required plant environmental conditions.
 2. The productivity of the crop is increased considerably.
 3. Superior quality produce can be obtained as they are grown under suitably controlled
environment.
 4. Gadgets for efficient use of various inputs like water, fertilizers, seeds and plant protection
chemicals can be well maintained in a green house.
 5. Effective control of pests and diseases is possible as the growing area is enclosed.
 6. Percentage of germination of seeds is high in greenhouses.
 7. The acclimatization of plantlets of tissue culture technique can be carried out in a green
house.

14.  8. Agricultural and horticultural crop production schedules can be planned to take
advantage of the market needs.
 9. Different types of growing medium like peat mass, vermiculate, rice hulls and
compost that are used in intensive agriculture can be effectively utilized in the
greenhouse.
 10. Export quality produce of international standards can be produced in a green house.
 11. When the crops are not grown, drying and related operations of the harvested
produce can be taken up utilizing the entrapped heat.
 12. Greenhouses are suitable for automation of irrigation, application of other inputs
and environmental controls by using computers and artificial intelligence techniques.
 13. Self-employment for educated youth on farm can be increased.

15. Disadvantages
 High Installation cost
Technical persons needed
Only for commercial crop
cultivation
Maintenance cost is high

16. Quonset type
Gable type

17. During summer season temperature 50-55℃

18. 9

20. TYPES OF GREENHOUSES
Greenhouse structures of various types are used for crop production.
Although there are advantages in each type for a particular
application, in general there is no single type of greenhouse, which
can be constituted as the best.
 Different types of greenhouses are designed to meet the specific
needs. The different types of greenhouses based on shape, utility,
material and construction are briefly given below:

21. Greenhouse Type Based On Shape:
1. For the purpose of classification, the uniqueness of cross section of the greenhouses can be
considered as a factor. The commonly followed types of greenhouses based on shape are:
2. Lean to type greenhouse.
3. Even span type greenhouse.
4. Uneven span type greenhouse.
5. Ridge and furrow type.
6. Saw tooth type.
7. Quonset greenhouse.
8. Interlocking ridges and furrow type Quonset greenhouse.
9. Ground to ground greenhouse.

23. Lean-to type greenhouse
 A lean-to design is used when a greenhouse is placed against the side of an
existing building. It is built against a building, using the existing structure for
one or more of its sides. It is usually attached to a house, but may be attached
to other buildings.
 The roof of the building is extended with appropriate greenhouse covering
material and the area is properly enclosed.
 It is typically facing south side.
 The lean-to type greenhouse is limited to single or double-row plant benches
with a total width of 7 to 12 feet. It can be as long as the building it is attached to.
 It should face the best direction for adequate sun exposure.

24. Lean-to type greenhouse
advantages
 It is usually close to available
electricity, water, and heat.
 It is a least expensive structure.
 This design makes the best use of
sunlight and minimizes the requirement
of roof supports.
disadvantages
 Limited space, limited light, limited
ventilation and temperature control.
 The height of the supporting wall limits
the potential size of the design.
 Temperature control is more difficult
because the wall that the greenhouse is
built on, may collect the sun's heat
while the translucent cover of the
greenhouse may lose heat rapidly.

26. Even span type greenhouse
 The even-span is the standard type and full-size structure, the two roof slopes are of
equal pitch and width.
 This design is used for the greenhouse of small size, and it is constructed on level
ground. It is attached to a house at one gable end. It can accommodate 2 or 3 rows of plant
benches.
 The cost of an even-span greenhouse is more than the cost of a lean-to type, but it has
greater flexibility in design and provides for more plants. Because of its size and greater
amount of exposed glass area, the even-span will cost more to heat.

27. The design has a better shape than a lean-to type for air circulation
to maintain uniform temperatures during the winter heating season.
A separate heating system is necessary unless the structure is very close
to a heated building. It will house 2 side benches, 2 walks, and a wide
center bench.
Several single and multiple span types are available for use in various
regions of India.
 For single span type the span in general, varies from 5 to 9 m, whereas
the length is around 24 m. The height varies from 2.5 to 4.3 m.

29. Uneven span type greenhouse
This type of greenhouse is
constructed on hilly terrain.
The roofs are of unequal
width; make the structure
adaptable to the side slopes
of hill.
This type of greenhouses is
seldom ( Rarely ) used
now-a-days as it is not
adaptable for automation.

30. Ridge and furrow type greenhouse
Designs of this type use two or more A-frame greenhouses connected to
one another along the length of the eave. The eave serves as furrow or gutter to
carry rain and melted snow away.
The side wall is eliminated between the greenhouses, which results in a
structure with a single large interior, Consolidation of interior space reduces
labour, lowers the cost of automation, improves personal management and
reduces fuel consumption as there is less exposed wall area through which heat
escapes.

31. The snow loads must be taken into the frame specifications of these
greenhouses since the snow cannot slide off the roofs as in case of
individual free standing greenhouses, but melts away.
In spite of snow loads, ridge and furrow greenhouses are effectively
used in northern countries of Europe and in Canada and are well
suited to the Indian conditions.

32. Ridge and furrow type greenhouse

33. Saw tooth type Greenhouse
 These are also similar to ridge
and furrow type greenhouses
except that, there is provision for
natural ventilation in this type.
 Specific natural ventilation flow
path develops in a saw- tooth type
greenhouse.

35. Quonset greenhouse
This is a greenhouse, where the pipe arches or trusses are supported by pipe purling
running along the length of the greenhouse.
 In general, the covering material used for this type of greenhouses is polyethylene.
 Such greenhouses are typically less expensive than the gutter connected greenhouses
and are useful when a small isolated cultural area is required.
These houses are connected either in free, standing style or arranged in an interlocking
ridge and furrow. In the interlocking type, truss members overlap sufficiently to allow a bed
of plants to grow between the overlapping portions of adjacent houses.
 A single large cultural space thus exists for a set of houses in this type, an arrangement that
is better adapted to the automation and movement of labour.

36. Interlocking ridge and furrow Quonset type.
use two or more Quonst
greenhouses connected
to one another along the
length

37. Greenhouse Type Based on Utility
 Classification can be made depending on the
functions or utilities. Of the different utilities,
artificial cooling and heating are more expensive and
elaborate. Hence based on this, they are classified in to
two types.
1. Greenhouses for active heating.
2. Greenhouses for active cooling.

39. Greenhouses for active heating
During the night time, air temperature inside greenhouse decreases. To
avoid the cold bite to plants due to freezing, some amount of heat has to be
supplied.
The requirements for heating greenhouse depend on the rate at which
the heat is lost to the outside environment.
Various methods are adopted to reduce the heat losses, viz., using
double layer polyethylene, thermo pane glasses (Two layers of factory
sealed glass with dead air space) or to use heating systems, such as unit
heaters, central heat, radiant heat and solar heating system.

40. Greenhouses for active cooling
During summer season, it is desirable to reduce the temperatures of
greenhouse than the ambient temperatures, for effective crop
growth.
 Hence suitable modifications are made in the green house so that large
volumes of cooled air is drawn into greenhouse, This type of
greenhouse either consists of evaporative cooling pad with fan or fog
cooling.
This greenhouse is designed in such a way that it permits a roof opening
of 40% and in some cases nearly 100%.

42. Greenhouse Type Based on Construction
The type of construction predominantly is influenced by structural
material, though the covering material also influences the type. Higher the
span, stronger should be the material and more structural members are
used to make sturdy tissues. For smaller spans, simple designs like hoops
can be followed. So based on construction, greenhouses can be classified
as
1. Wooden framed structure.
2. Pipe framed structure.
3. Truss framed structure.

44. Wooden framed structures
 In general, for the greenhouses with span less
than 6 m, only wooden framed structures are used.
Side posts and columns are constructed of wood
without the use of a truss.
 Pine wood is commonly used as it is
inexpensive and possesses the required strength.
 Timber locally available, with good strength,
durability and machinability also can be used for
the construction.

45. Pipe framed Greenhouse:-
 Pipes are used for construction
of greenhouses, when the clear
span is around 12m.
 In general, the side posts,
columns, cross ties and purlins are
constructed using pipes.
 In this type, the trusses are
not used.

47. Truss framed structures
 If the greenhouse span is greater than or equal to 15m, truss frames are used.
Flat steel, tubular steel or angular iron is welded together to form a truss
encompassing rafters, chords and struts.
 Struts are support members under compression and chords are support members
under tension. Angle iron purlins running throughout the length of greenhouse are
bolted to each truss.
Columns are used only in very wide truss frame houses of 21.3 m or more.
Most of the glass houses are of truss frame type, as these frames are best suited
for pre-fabrication.

49. Greenhouse Type Based on Covering Material
Covering materials are the major and important component of the greenhouse
structure.
Covering materials have direct influence on the greenhouse effect inside the structure
and they alter the air temperature inside the house.
 The types of frames and method of fixing also varies with the covering material.
Based on the type of covering materials, the greenhouses are classified as
1. Glass greenhouses
2. Plastic film greenhouses
3. Rigid panel greenhouses

54. Glass Green house:-
 Only glass greenhouses with glass as the
covering material existed prior to 1950.
 Glass as covering material has the advantage of
greater interior light intensity.
 These greenhouses have higher air infiltration
rate which leads to lower interior humidity
and better disease prevention.
 Lean-to type, even span, ridge and furrow type
of designs are used for construction of glass
greenhouse.

55. Plastic film greenhouses
 Flexible plastic films including polyethylene, polyester and polyvinyl chloride are used as
covering material in this type of greenhouses.
 Plastics as covering material for greenhouses have become popular, as they are cheap
and the cost of heating is less when compared to glass greenhouses.
 The main disadvantage with plastic films is its short life.
 For example, the best quality ultraviolet (UV) stabilized film can last for four years only.
 Quonset design as well as gutter-connected design is suitable for using this covering
material.

56. Rigid panel greenhouses
 Polyvinyl chloride rigid panels, fibre glass-reinforced plastic, acrylic and
polycarbonate rigid panels are employed as the covering material in the Quonset type
frames or ridge and furrow type frame.
 This material is more resistant to breakage and the light intensity is uniform
throughout the greenhouse when compared to glass or plastic.
 High grade panels have long life even up to 20 years.
 The main disadvantage is that these panels tend to collect dust as well as to harbor
algae, which results in darkening of the panels and subsequent reduction in the light
transmission. There is significant danger of fire hazard.

57. Greenhouse Type Based on Cost of Construction
Based on the cost of construction involved :
1.High cost Green House
2.Medium cost Green House
3.Low cost Green House

58. Low cost Green House
Naturally controlled
Shading nets
Supporting structure
(wood, GI pipe,
polyethylene films

59. Medium Cost
Pads, fans, shade nets, heating
to control environment
Supporting structure (GI or
aluminium pipes)
UV Sterilised plastic film

60. High Cost
 Air conditioning, Computer
Control Environment
Uv steel, plastic films, fan,pad,drip

61. 10

62. Plant needs
 Temperature :- 18-30℃
 Humidity :- 50-70%
 Co2 :- 300-800ppm(Parts per Milion)
 Sun light :- wave length 400-700 nm(nano meter)
Micro Nutrients

63. Plant response to greenhouse environments
 The productivity of a crop is influenced not only by its heredity but
also by the microclimate around it. The components of crop
microclimate are light, temperature, air compositions and the nature of
the root medium. In open fields, only manipulation of nature of the
root medium by tillage, irrigation and fertilizer application is
possible. The closed boundaries in greenhouse permit control of any one
or more of the components of the micro climate.

64. Light
The visible light of the solar radiation is a source of energy for plants. Light
energy, carbon dioxide (Co2) and water all enter in to the process of
photosynthesis through which carbohydrates are formed.
The production of carbohydrates from carbon dioxide and water in the
presence of chlorophyll, using light energy is responsible for plant growth
and reproduction.
The rate of photosynthesis is governed by available fertilizer elements,
water, carbon dioxide, light and temperature. The photosynthesis
reaction can be represented as follows Chlorophyll
Co2 + water+ light energy --------------------˃ carbohydrates + oxygen
Plant nutrients

65.  Considerable energy is required to reduce the carbon that is combined with
oxygen in CO2 gas to the state in which it exists in the carbohydrate. The light
energy thus utilized is trapped in the carbohydrate.
 If the light intensity is diminished, photosynthesis slows down and hence the
growth. If higher than optimal light intensities are provided, growth again slows
down because of the injury to the chloroplasts.
Chlorophyll
Co2 + water+ light energy --------------------˃ carbohydrates + oxygen
Plant nutrients

66.  The light intensity is measured by the international unit known as Lux. It is direct
illumination on the surrounding surface that is one meter from a uniform point source of 1
international candle.
 Green house crops are subjected to light intensities varying from 129.6klux on clear
summer days to 3.2 Klux on cloudy winter days. For most crops, neither condition is
ideal.
 Many crops become light saturated, in other words, photosynthesis does not increase at light
intensities higher than 32.2klux. Rose and carnation plants will grow well under summer
light intensities.
 In general, for most other crops foliage is deeper green if the greenhouse is shaded to the
extent of about 40% from mid spring (May) to mid fall (August and September). Thus, it is
apparent that light intensity requirements of photosynthesis are vary considerably from crop
to crop.

67.  Light is classified according to its wave length in nanometers (nm). Not all light useful in
photosynthesis process.
 UV light is available in the shorter wavelength range, i.e less than 400nm. Large of
quantities of it is harmful to the plants. Glass screens are opaque to the most UV light and
light below the range of 325nm.
 Visible and white light has wavelength of 400 to 700nm.Far red light (700 to 750nm)
affects plants, besides causing photosynthesis. Infrared rays of longer wavelengths are not
involved in the plant process. It is primarily, the visible spectrum of light that is used in
photosynthesis. In the blue and red bands, the photosynthesis activity is higher, when the
blue light (shorter wavelength) alone is supplied to plants, the growth is retarded, and the
plant becomes hard and dark in colour. When the plants are grown under red light (longer
wavelength), growth is soft and internodes are long, resulting in tall plants. Visible light of
all wavelengths is readily utilized in photosynthesis.

68. Temperature
 Temperature is a measure of level of the heat present. All crops have temperature range
in which they can grow well. Below this range, the plant life process stop due to ice
formation within the tissue and cells are possibly punctured by ice crystals. At the upper
extreme, enzymes become inactive, and again process essential for life cease. Enzymes
are biological reaction catalyst and are heat sensitive. All biochemical reactions in the
plant are controlled by the enzymes. The rate of reactions controlled by the enzyme
often double or triple for each rise of temperature by 100C, until optimum temperature is
reached. Further, increase in temperature begins to suppress the reaction and finally stop
it.

69. As a general rule, green house crops are grown at a day temperature,
which are 3 to 60C higher than the night temperature on cloudy days
and 80C higher on clear days. The night temperature of green house
crops is generally in the range of 7 to 210C. Primula, mathiola incana
and calceolaria grow best at 70C, carnation and cineraria at 100C,
rose at 160C, chrysanthemum and poinsettia at 17 to 180C and
African violet at 21 to 220C.

70. Relative humidity
 As the green house is a closed space, the relative humidity of the green house air
will be more when compared to the ambient air, due to the moisture added by the
evapo-transpiration process. Some of this moisture is taken away by the air
leaving from the green house due to ventilation. Sensible heat inputs also lower
the relative humidity of the air to some extent. In order to maintain the desirable
relative humidity levels in the green houses, processes like humidification or
dehumidification are carried out. For most crops, the acceptable range of relative
humidity is between 50 to 80%. However for plant propagation work, relative
humidity up to 90% may be desirable.

71. In summer, due to sensible heat addition in the daytime, and in
winters for increasing the night time temperatures of the green house
air, more sensible heat is added causing a reduction in the relative
humidity of the air. For this purpose, evaporative cooling pads and
fogging system of humidification are employed. When the relative
humidity is on the higher side, ventilators, chemical dehumidifiers
and cooling coils are used for de- humidification.

72. Ventilation
 A green house is ventilated for either reducing the temperature of the green house
air or for replenishing carbon dioxide supply or for moderating the relative
humidity of the air. Air temperatures above 350C are generally not suited for the
crops in green house. It is quite possible to bring the green house air temperature
below this upper limit during spring and autumn seasons simply by providing
adequate ventilation to the green house. The ventilation in a green house can
either be natural or forced. In case of small green houses (less than 6m wide)
natural ventilation can be quite effective during spring and autumn seasons.
However, fan ventilation is essential to have precise control over the air
temperature, humidity and carbon dioxide levels.

73. Carbon dioxide
 Carbon is an essential plant nutrient and is present in the plant in greater quantity than any other
nutrient. About 40% of the dry matter of the plant is composed of carbon. Under normal
conditions, carbon dioxide (CO2) exits as a gas in the atmosphere slightly above 0.03% or
345ppm. During the day, when photosynthesis occurs under natural light, the plants in a green
house draw down the level of Co2 to below 200ppm. Under these circumstances, infiltration or
ventilation increases carbon dioxide levels, when the outside air is brought in, to maintain the
ambient levels of CO2. If the level of CO2 is less than ambient levels, CO2 may retard the plant
growth. In cold climates, maintaining ambient levels of CO2 by providing ventilation may be
un- economical, due to the necessity of heating the incoming air in order to maintain proper
growing temperatures. In such regions, enrichment of the green house with CO2 is followed.
The exact CO2 level needed for a given crop will vary, since it must be correlated with other
variables in greenhouse production such as light, temperature, nutrient levels, cultivar and
degree of maturity. Most crops will respond favorably to Co2 at 1000 to 1200 ppm.